id-Linux Command

id command- Print real and effective user id (uid) and group id (gid)

Syntax: id [options]... [username]

Description: The id command lists the real and effective user IDs and the group IDs of the user associated with the current process. This is the counterpart to the $UID, $EUID, and $GROUPS internal Bash variables.
The id command shows the effective IDs only when they differ from the real ones.